|Publication number||US6747439 B2|
|Application number||US 10/317,325|
|Publication date||Jun 8, 2004|
|Filing date||Dec 12, 2002|
|Priority date||May 28, 2002|
|Also published as||DE10223557A1, EP1367686A2, EP1367686A3, US20030222622|
|Publication number||10317325, 317325, US 6747439 B2, US 6747439B2, US-B2-6747439, US6747439 B2, US6747439B2|
|Original Assignee||Braun Gmbh|
|Export Citation||BiBTeX, EndNote, RefMan|
|Patent Citations (9), Referenced by (4), Classifications (9), Legal Events (6)|
|External Links: USPTO, USPTO Assignment, Espacenet|
This application claims priority to German Patent Application No. DE 102 23 557.0, filed May 28, 2002, which is incorporated herein by reference in its entirety.
This invention relates to batteries, and more particularly to rechargeable batteries.
DE 199 05 550 depicts a method for determining or indicating the charge state of a primary or secondary battery. Essentially, the battery is discharged so that only a minimum residual charge remains. The time required for the battery to be discharged (i.e., discharge time) is measured by a connected consumer measuring the time required for the battery voltage to drop to a first voltage threshold value, assuming the consumer has an essentially constant current consumption over an average time period. When the first voltage threshold value has been reached, it is reduced by an amount that depends on the discharge time measured. If the consumer further discharges the battery, so that the battery voltage drops still further, reaching the reduced voltage threshold value is an indicator for the discharge of the battery to a particular residual charge, i.e. for the presence of a low charge state of the battery.
DE 44 09 736 depicts a method and a device for caring for an accumulator (i.e., a rechargeable battery) incorporated in an accumulator-operated device wherein the memory effect is counteracted. In this known method, every few months the accumulator is automatically fully discharged and then fully recharged again. This accumulator care is only carried out if the accumulator-operated device is connected to the electrical outlet by means of a charging set, and if recharging after discharging is therefore certain. If the device is operated as described above, i.e. if the accumulator is always discharged for only a few minutes before being completely charged again, then accumulator care at shorter intervals would be desirable. On the other hand, accumulator care can be entirely done without if during operation of the device the accumulator is always first completely discharged before it is charged again.
The present invention includes methods and devices for the conditioning of a rechargeable battery in a manner reflecting the rechargeable battery's state at the time the conditioning is performed.
Conditioning is intended to prevent as far as possible the changes in battery characteristics otherwise caused by ageing and by the memory effect.
In several aspects, the invention features a method of conditioning a rechargeable battery. In one aspect the invention features a method of conditioning a rechargeable battery, including providing a fully charged rechargeable battery and measuring a discharge time for which the voltage of the battery takes to decrease to a voltage threshold value. The discharge time is compared to a reference value, and if the discharge time is less than the reference value, the battery is shorted through a discharge load to further discharge the battery.
In the present application, discharge time does not refer to the time during which the battery voltage drops only as a result of self-discharge of the battery, but instead, discharge time refers to the time it takes for the battery to be discharged by way of a connected consumer, for example a device being operated by the consumer
In some embodiments, in addition to the discharge time, the current which flows during discharge is also measured, and from it, the charge quantity taken from the battery is determined. The charge quantity determined is compared with a comparison value, and if the battery voltage has dropped to the voltage threshold value before the charge quantity which corresponds to the comparison value has been taken from the battery, the battery is fully discharged.
In other embodiments, the time which has passed since the battery voltage last dropped to the voltage threshold value is also measured. If for example a device operated by the rechargeable battery is always used for a few minutes only before the battery is fully recharged again following use, the battery voltage is unlikely to drop to the voltage threshold value for some time. The same applies if, for an extended period, the device is not used at all or is seldom used. If this time exceeds a specified maximum time, in certain embodiments, the battery is discharged until the battery voltage drops to the voltage threshold value, and the discharge time which has passed since full load or battery change, or the charge quantity which has been taken since full load or battery change, is measured; the measured value is compared with the reference value or to the comparison value, and, if necessary, the battery is fully discharged. If in the case of exceeding the maximum period, the battery voltage is already below the voltage threshold value, the battery is fully discharged. Accordingly, the rechargeable battery is only fully discharged if this is necessary for maintaining the full service life of the battery, i.e. for getting rid of the memory effect. On the other hand, battery conditioning is not required if, during operation, the battery gets discharged frequently enough to the extent that the battery voltage drops below the voltage threshold value before the battery is charged again.
In another embodiment, the time is also measured which has passed since the battery was last charged or changed. If this time exceeds a minimum time and if during this time the battery voltage has dropped to the voltage threshold value as a result of self-discharge alone, then a display is activated which signals ageing, i.e. the need for a change of battery.
In another embodiment, the battery is recharged after discharge. In still another embodiment, directly after recharging, a complete battery conditioning cycle including complete discharge and subsequent recharge is performed. If the discharge time measured or the charge quantity taken is again below the reference value or comparison value, this indicates an aged battery. The display which signals the necessity for changing the battery is then activated.
This additional battery care cycle is preferably carried out by automatic discharge of the battery via a load resistor and automatic recharge. However, it can also be carried out by the user through normal operation of the device.
One aspect of the invention features an electrical appliance, which includes a discharge load and a rechargeable battery for powering the electrical appliance, which is connected through a switch to the discharge load and used for powering the discharge load. Additionally, the electrical appliance includes a connector for connecting the appliance to an external source of electrical energy, and an electronic circuit that discharges the rechargeable battery by shorting the rechargeable battery through the discharge load only while the appliance is connected to the external energy source.
In some embodiments, the electronic circuit measures a discharge time for which the voltage of the battery takes to decrease to a voltage threshold value, compares the discharge time to a reference value; and if the discharge time is less than the reference value, shorts the battery through the discharge load to further discharge the battery.
In some embodiments, the electronic circuit measures a current flow during discharge, determines a charge quantity from the measured current flow during the measured discharge time, compares the determined charge quantity with the charge quantity of a reference value, and if the battery voltage drops to the voltage threshold value before the charge quantity corresponding to the reference value is released, shorts the battery through the discharge load to further discharge the battery.
In some embodiments, shorting the battery through the discharge load fully discharges the battery.
In some embodiments, the current flow is measured while also measuring the discharge time.
In some embodiments, the electronic circuit measures a first time interval which has passed since the battery voltage last dropped to the voltage threshold value, determines whether the first time interval exceeds a maximum reference time, and if the first time interval exceeds the maximum reference time, shorts the battery through the discharge load to discharge the battery until the battery voltage drops to the voltage threshold value.
In some embodiments, the electronic circuit recharges the battery after shorting the rechargeable battery.
In some embodiments, the discharge load is a resistor disposed within the appliance.
In some embodiments, the electronic appliance is an electrical shaver or an electric toothbrush.
The details of one or more embodiments of the invention are set forth in the accompanying drawings and the description below. Other features, objects, and advantages of the invention will be apparent from the description and drawings, and from the claims.
FIG. 1 is a graph depicting typical discharge characteristics of a rechargeable battery
FIG. 2 is a graph depicting an example of the discharge characteristics of a rechargeable battery.
FIG. 3 depicts an appliance having a rechargeable battery.
Like reference symbols in the various drawings indicate like elements.
FIG. 1 shows typical discharge characteristics of a rechargeable battery. The top curve shows the time-dependent gradient of the voltage of a new battery which, starting from its fully charged state (voltage 1.35 V), is completely discharged (voltage<1 V) over a period of time of 50 minutes. If a battery is operated for a significant period of time (e.g., several years) in such a way that it is only discharged for a few minutes before it is fully charged again, then the lowest gradient shown in FIG. 1 results when the battery is fully discharged. If the battery is then repeatedly fully charged and fully discharged several times, then the middle gradient shown in FIG. 1 results. The difference between the top gradient and the middle gradient is due to ageing, whereas the difference between the bottom gradient and the middle gradient is due to the memory effect.
Referring to FIG. 3, the methods and devices described herein can be applied to battery-operated devices 10, for example an electrical shaver or an electrical toothbrush that includes a built-in charging circuit and which can, for example, be recharged using a cable 12 connected to an electrical outlet 14 or a separate charging set. Charging is preferably carried out automatically by an electronic circuit, for example a microcontroller 16, incorporated in the device. Voltage threshold value, maximum time, minimum time and reference value or comparison value are all determined depending on the typical current consumption of the device 10, the capacity of the battery 18 used in the device, the minimum operating voltage required by the device 10, and, if applicable, further parameters of the battery 18 and/or of the temperature. These values are stored in the microcontroller 16. In the example shown in FIG. 2, the voltage threshold value is 1.15 V and the reference value for the discharge time is 7.4 mm. In order to implement the method according to the invention, i.e. in order to discharge the battery 18 for the purpose of battery conditioning without the need for action by a user, the device must also include a load, for example a resistor 20, as well as a switch 22 (preferably an electronic switch), which is controlled by the electronic circuit. Additionally, the battery can be connected to the load by this switch and can be discharged accordingly.
The microcontroller 16 detects the charged state of the battery 18, for example by comparing the actual battery voltage with the nominal voltage of the battery, which is also stored in the microcontroller 16. An exchange of the battery 18, can result in a microcontroller 16 reset and can therefore also be easily detected. In the case of devices where the microcontroller 16 also controls the charging action of the battery 18, the fully charged state of the battery 18 is preferably recognized such that a condition for completion of the charging action, which is known per se, is met.
In the cases where the battery-operated device includes a display for the charge state of the rechargeable battery, then, after automatic discharge of the battery, a user can ensure recharge by means of the charge state display. It is, however, particularly advantageous if the electronic circuit includes a device that detects the connection of the device with an external source of electrical energy, for example an electrical outlet or a charging set that is ready for operation, which allows the battery to be recharged again. If the device is connected to the external energy source, the battery is preferably recharged automatically. It is advantageous if the battery is only automatically discharged if it is connected to the external energy source.
In order to improve the accuracy of the method, the voltage threshold value can be determined so as to be temperature-compensated, i.e. it is changed depending on the temperature.
A number of embodiments of the invention have been described. Nevertheless, it will be understood that various modifications may be made without departing from the spirit and scope of the invention. Accordingly, other embodiments are within the scope of the following claims.
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|Citing Patent||Filing date||Publication date||Applicant||Title|
|US7825615 *||Nov 2, 2010||Glj, Llc||Intelligent motorized appliances with multiple power sources|
|US8138721 *||May 18, 2009||Mar 20, 2012||Samsung Sdi Co., Ltd.||Battery pack and charging method for the same|
|US20090096399 *||Oct 16, 2007||Apr 16, 2009||Yung Chen||Intelligent motorized appliances with multiple power sources|
|US20090295332 *||Dec 3, 2009||Samsung Sdi Co., Ltd.||Battery pack and charging method for the same|
|U.S. Classification||320/133, 320/155|
|International Classification||H01M10/44, H01M10/48, H02J7/00|
|Cooperative Classification||H02J7/0075, H02J7/0073|
|European Classification||H02J7/00M10B, H02J7/00M10B1|
|Mar 24, 2003||AS||Assignment|
Owner name: BRAUN GMBH, GERMANY
Free format text: ASSIGNMENT OF ASSIGNORS INTEREST;ASSIGNOR:FRANKE, MICHAEL;REEL/FRAME:013873/0717
Effective date: 20030313
|Dec 10, 2007||FPAY||Fee payment|
Year of fee payment: 4
|Dec 17, 2007||REMI||Maintenance fee reminder mailed|
|Jan 23, 2012||REMI||Maintenance fee reminder mailed|
|Jun 8, 2012||LAPS||Lapse for failure to pay maintenance fees|
|Jul 31, 2012||FP||Expired due to failure to pay maintenance fee|
Effective date: 20120608